1. Field of the Invention
The present invention relates to a scrambling apparatus for subjecting information signals such as video signals, audio signals and general data signals to scrambling processing.
2. Description of the Related Art
In chargeable broadcasting by radio transmission such as what is called pay television, for instance, signals are subjected to scrambling processing before they are transmitted in order to prevent a non-subscriber, who has not made a contract for payment with a broadcasting industrial company from viewing the programs. Furthermore, when a special program needs extra charge or when the receivable programs vary according to the conditions of a contract, scrambling processing operations must be varied with the program.
When signals are subjected to scrambling process, they are often controlled by a pseudo-random signal system (scrambling system) and, on the reception side, unscrambling processing is executed by using the same signal system (unscrambling system) as that on the transmission side so as to restore the signals to original signals. A scramble key is transmitted to the random signal system. It is necessary to control the unscrambling processing according to the corresponding conditions of contracts of subscriber such as the type of services, the term of a contract and the sum of money paid and the information related thereto is transmitted to a receiving apparatus.
A conventional scrambling apparatus needs an external computer system connected thereto for the management of the subscribers and scrambling processing control in accordance with the conditions of the contract.
In recent years, for instance, the above-described scrambling apparatus and other broadcasting appliances have often been installed in a vehicle, etc. as a broadcasting station, which is used for the purpose of a sport relay broadcast, a theater relay broadcast, ENG or the like on the spot or while driving the vehicle In such a small space as a broadcasting station in a vehicle, however, the size of the external computer system connected to the scrambling apparatus is a problem. Since the above-described various scramble controlling operations are also executed by operating an inputting device such as a keyboard, the controlling operations are difficult or troublesome within a vehicles.
To solve this problem, the above-described various scramble control may be executed by internally mounting an FDD (floppy disk drive) on the scrambling apparatus and replacing the disc as needed. However, this method still suffers from following problems. Since an FDD is generally susceptible to vibration and shock, it is not fit to be installed in a vehicle. In addition, this method fundamentally requires an DOS (disk operating system) so as to control reading and writing operations for the disk which leads to increase the cost of the software.
If the information on the scrambling operation, the status information related to the operation during the scrambling operation of the scrambling apparatus, etc. are recorded into a recording medium, they are useful not only for the control of the progress of a program and the management of subscribers but also as data for the maintenance and checking of the scrambling apparatus and a lead in finding the troubled part when the scrambling apparatus gets out of order. A floppy disk is, however, unsuitable as such a medium for recording scrambling operation, because it has the above-described problems such as the susceptibility to vibration and shock or expensive software